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| <title>Boost.Python - <wrapper.hpp></title> |
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| <h3><a href="../../../../index.htm"><img height="86" width="277" alt= |
| "C++ Boost" src="../../../../boost.png" border="0"></a></h3> |
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| <td valign="top"> |
| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 align="center">Header <wrapper.hpp></h2> |
| </table> |
| <hr> |
| |
| <h2>Contents</h2> |
| |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a></dt> |
| |
| <dt><a href="#classes">Classes</a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#override-spec">Class template |
| <code>override</code></a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#override-spec-synopsis">Class |
| <code>override</code> synopsis</a></dt> |
| |
| <dt><a href="#override-spec-observers">Class |
| <code>override</code> observer functions</a></dt> |
| </dl> |
| </dd> |
| |
| <dt><a href="#wrapper-spec">Class template |
| <code>wrapper</code></a></dt> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#wrapper-spec-synopsis">Class <code>wrapper</code> |
| synopsis</a></dt> |
| |
| <dt><a href="#wrapper-spec-observers">Class |
| <code>wrapper</code> observer functions</a></dt> |
| </dl> |
| </dd> |
| </dl> |
| </dd> |
| |
| <dt><a href="#examples">Example(s)</a></dt> |
| </dl> |
| <hr> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| |
| <p>To wrap a class <code>T</code> such that its virtual functions can be |
| "overridden in Python"—so that the corresponding method of a Python |
| derived class will be called when the virtual function is invoked from |
| C++—you must create a C++ wrapper class derived from ``T`` that |
| overrides those virtual functions so that they call into Python. This |
| header contains classes that can be used to make that job easier.</p> |
| |
| <h2><a name="classes"></a>Classes</h2> |
| |
| <h3><a name="override-spec"></a>Class <code>override</code></h3> |
| |
| <p>Encapsulates a Python override of a C++ virtual function. An |
| <code>override</code> object either holds a callable Python object or |
| <code>None</code>.</p> |
| |
| <h4><a name="override-spec-synopsis"></a>Class <code>override</code> |
| synopsis</h4> |
| <pre> |
| namespace boost |
| { |
| class override : object |
| { |
| public: |
| <i>unspecified</i> operator() const; |
| template <class A0> |
| <i>unspecified</i> operator(A0) const; |
| template <class A0, class A1> |
| <i>unspecified</i> operator(A0, A1) const; |
| ... |
| template <class A0, class A1, ...class A<i>n</i>> |
| <i>unspecified</i> operator(A0, A1, ...A<i>n</i>) const; |
| }; |
| }; |
| </pre> |
| |
| <h4><a name="override-spec-observers"></a>Class <code>override</code> |
| observer functions</h4> |
| <pre> |
| <i>unspecified</i> operator() const; |
| template <class A0> |
| <i>unspecified</i> operator(A0) const; |
| template <class A0, class A1> |
| <i>unspecified</i> operator(A0, A1) const; |
| ... |
| template <class A0, class A1, ...class A<i>n</i>> |
| <i>unspecified</i> operator(A0, A1, ...A<i>n</i>) const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Effects:</b> If <code>*this</code> holds a callable Python |
| object, it is invoked with the specified arguments in the manner |
| specified <a href="callbacks.html">here</a>. Otherwise, throws <code><a |
| href="errors.html#error_already_set-spec">error_already_set</a></code> |
| .</dt> |
| |
| <dt><b>Returns:</b> An object of unspecified type that holds the Python |
| result of the invocation and, when converted to a C++ type |
| <code>R</code>, attempts to convert that result object to |
| <code>R</code>. If that conversion fails, throws <code><a href= |
| "errors.html#error_already_set-spec">error_already_set</a></code> |
| .</dt> |
| </dl> |
| |
| <h3><a name="wrapper-spec"></a>Class template <code>wrapper</code></h3> |
| |
| <p>Deriving your wrapper class from both ``T`` <i>and</i> |
| ``wrapper<T> makes writing that derived class easier.</p> |
| |
| <h4><a name="wrapper-spec-synopsis"></a>Class template |
| <code>wrapper</code> synopsis</h4> |
| <pre> |
| namespace boost |
| { |
| class wrapper |
| { |
| protected: |
| override get_override(char const* name) const; |
| }; |
| }; |
| </pre> |
| |
| <h4><a name="wrapper-spec-observers"></a>Class <code>wrapper</code> |
| observer functions</h4> |
| <pre> |
| override get_override(char const* name) const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| <dt><b>Requires:</b> <code>name</code> is a <a href= |
| "definitions.html#ntbs">ntbs</a>.</dt> |
| |
| <dt><b>Returns:</b> If <code>*this</code> is the C++ base class |
| subobject of a Python derived class instance that overrides the named |
| function, returns an <code>override</code> object that delegates to the |
| Python override. Otherwise, returns an <code>override</code> object |
| that holds <code>None</code>.</dt> |
| </dl> |
| |
| <h2><a name="examples"></a>Example</h2> |
| <pre> |
| #include <boost/python/module.hpp> |
| #include <boost/python/class.hpp> |
| #include <boost/python/wrapper.hpp> |
| #include <boost/python/call.hpp> |
| |
| using namespace boost::python; |
| |
| // Class with one pure virtual function |
| struct P |
| { |
| virtual ~P(){} |
| virtual char const* f() = 0; |
| char const* g() { return "P::g()"; } |
| }; |
| |
| struct PCallback : P, wrapper<P> |
| { |
| char const* f() |
| { |
| #if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) // Workaround for vc6/vc7 |
| return call<char const*>(this->get_override("f").ptr()); |
| #else |
| return this->get_override("f")(); |
| #endif |
| } |
| }; |
| |
| // Class with one non-pure virtual function |
| struct A |
| { |
| virtual ~A(){} |
| virtual char const* f() { return "A::f()"; } |
| }; |
| |
| struct ACallback : A, wrapper<A> |
| { |
| char const* f() |
| { |
| if (override f = this->get_override("f")) |
| #if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) // Workaround for vc6/vc7 |
| return call<char const*>(f.ptr()); |
| #else |
| return f(); |
| #endif |
| |
| return A::f(); |
| } |
| |
| char const* default_f() { return this->A::f(); } |
| }; |
| |
| BOOST_PYTHON_MODULE_INIT(polymorphism) |
| { |
| class_<PCallback,boost::noncopyable>("P") |
| .def("f", pure_virtual(&P::f)) |
| ; |
| |
| class_<ACallback,boost::noncopyable>("A") |
| .def("f", &A::f, &ACallback::default_f) |
| ; |
| } |
| </pre> |
| |
| <p>Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
| 31 October, 2004 |
| <!--webbot bot="Timestamp" endspan i-checksum="39359" --> |
| |
| |
| <p><i>© Copyright <a href="http://www.boost.org/people/dave_abrahams.htm">Dave |
| Abrahams</a> 2004</i> Distributed under the Boost Software License, |
| Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt)</p> |
| |